1. Field
The present invention relates to devices and systems useful as a powertrain of a vehicle, and methods for controlling such a powertrain.
2. Description of the Related Art
Existing vehicles powered by an internal combustion engine use a multi-ratio transmission to modify the torque produced by the internal combustion engine and then to output the modified torque to the drive wheels of the vehicle. It can be advantageous to determine the real-time value of the torque output by the transmission for certain performance enhancement systems and methods such as, but not limited to, traction control, dynamic stability control, or all-wheel-drive control.
Systems and methods that can sense or otherwise determine the actual torque output of the transmission in real time can be complex in design, expensive to assemble and/or maintain, and/or lack sufficient durability and/or reliability for daily use in certain weather conditions for a vehicle. These and other factors can outweigh the benefits or advantages that such systems and methods can provide.
Thus, systems and methods have been developed that can estimate the actual torque output of the transmission using systems and components that can be used advantageously on a vehicle. These conventional systems and methods typically rely on data from any one or combination of, an engine map, transmission gear ratio value(s), transmission shift status, a torque converter map, and driveline losses to estimate the real-time modified torque. These conventional systems and methods also can utilize other parameters known in the art when estimating the real-time torque output by the transmission.
Certain of these conventional systems and methods can provide an estimation of the real-time torque output by the transmission. However, the estimation may be inaccurate during a shift (up or down) from a one gear ratio to another gear ratio. In multi-ratio transmissions utilizing a plurality of gears to provide the plurality of gear ratios, a plurality of clutches are used to selectively engage/disengage certain combinations of the gears in order to couple the transmission output to the transmission input via the appropriate gear ratio. Typically, more than one clutch in the transmission is actuated to select and deselect the relevant gear ratio. Any variation in the actuation rate and actuation pressure of each clutch involved in the shift can cause a fluctuation in the torque output by the transmission. The actuation rate and pressure of each clutch can also vary over the lifetime of the transmission. Thus, it can be difficult to accurately model the transmission of torque through each relevant clutch during each operation of the relevant clutch(es) accurately and reliably over the lifetime of the vehicle even when subject to reasonable maintenance of the vehicle.
This inaccuracy can be exaggerated when the estimated torque is utilized by a controller via a control algorithm that distributes torque individually between wheels of a powertrain. This distribution can be effected, for example, between the left and right wheels in a two-wheel drive powertrain, between the front and rear wheels in an all-wheel drive powertrain, or between the left rear wheel and the right rear wheel in an all-wheel drive powertrain. Thus, there is a need to provide a control system and method to control a powertrain with improved accuracy for estimating available torque during a shift operation in the transmission.